Craftsman 12 gal, 2.5 HP compressor bogs on startup

by Patrick
(Orlando Fla.)

System builds up to 80 PSI and I shut it off manually. On trying restart the motor bogs down as if it is bucking the load within the tank. Im guessing its the check valve. Please advise.


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Sep 30, 2014
Craftsman bogs on startup
by: Bill

Based on what you are telling me, I don't suspect the check valve, but rather, the unloader valve.

Read the page on it, pull it out, clean it, replace it, and see if that solves your problem.

Make sure you empty the tank and pull the power cord before you work on your compressor.

Cheers,

Bill

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craftsman 30 gal 6 horsepower blows breakers

i was using it the other day and when i was using it it was suposed to kick on and fill back up with air but it didnt so i went over to see what was wrong with it and realized the breaker was kicked off so i put it back on and plugged it in and it turned on and 3 seconds later it kicked off again any tips? please help me?
_______________________

First thing to do is turn it off, drain all the air from the tank, close the drain valve again, and turn it on.

Does is start and run, or does it kick off the breaker? Post your response as a comment here please so I can follow our discussion.

Cheers,

Bill

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Sep 15, 2011
comment to awnser
by: becky

it like trys to fill up it just goes for 4 seconds and kicks off the breaker

_________________

If nothing else has changed, power supply, mechanical issue, then your symptoms suggest that the start capacitor or the motor is failing or has failed.

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older craftsman 12 gallon air compressor ~ Reset button pops upon re-filling tank

Not sure if this is the right area, But i have an older craftsman 12 gallon air compressor that i got for free, that for some reason, Plug it in and it will run and fill to correct pressure and then cut off.

Then, as you're using it, When it drops below pressure, It goes to re-start, lights dim, motor turns (slower then normal) will go maybe 5 rotations and then click, reset button on motor clicks off.

Push reset button, same thing.

Drain all air from tank, hit reset starts up fine and runs and fills tank to capacity.

(Yes, unload valve is releasing air, i hear the hiss)

OR, If i plug it in (from 0 psi), and let it fill to any pressure, pull the plug, press unloader valve (hear the hiss), and go to plug it back in, Same deal. turns over few times then off.

Things i have already tried, new cord, checked pump, checked stopper valve (I think thats what it is, The one way valve going from compressor to tank)

What could be wrong??

I dont think its the motor, why would it be able to run no problem at 0 psi-120psi, but anything past 0 on startup it cant?

I've been getting very frustrated with this compressor and don't know what to do.

So far I'm only into it $12 bucks for a new belt and a lot of aggravating hours of work.

Its a 1hp motor belt driven to a two piston pump.
110v

Any help would be great!

______________________
Bill says...

Glad to help, if I can, and I too wish I had some BigMoney!

Here's what I think. You have a pretty good power circuit to your compressor, and you don't have a lot of other electrical "stuff" interfering with getting a good current flow to your compressor.

Your current flow is soooooo good, that even though most electric motors need an electrical boost to start, yours is able to pull enough power from the supply circuit to start when there is no load.

However, add some load (pressure in the system makes the motor work harder) and the motor needs more amperage on start up, and your system isn't providing that.

I think that if you check your motor capacitor, that will be your problem. The capacitor is what is supposed to give your electric motor the boost it needs on start up. Without the capacitor adding the boost, your motor pulls too many amps, and pops the breaker.

Cheers,

Bill


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Jan 02, 2011
me again
by: Anonymous

Hey, This might be off topic, But since this compressor went down, I picked up 2 more. One kobalt 22 g digital compressor that works. And a newer 15G craftsman oil less compressor.

I figured id hook the two of them together and get a total of 37G's. And maybe even the old craftsman 12G tank with it for 49G's.

But, Before i do all of that. I bought the craftsman 15g, for cheap, and it turns out that the connecting rod snapped, i took it apart, and the rod snapped off right before the piston, and dinged up two sides of the sleeve. I was wondering if i could replace the piston/rod (one piece) and sleeve and maybe the valves (Theres a square with the in/out valves on it, and the in valves wernt connected anymore)
Where would i find these pieces, and would it be worth replacing? Id love to be bale to run both together, because the kobalt fills up SO slow.

And that leads to my other question, The kobalt compressor takes forever to fill the tank (again oilless), I was wondering if there was anything i could do short of replacing the pump to make it fill a bit faster?

Thanks for the help!


Dec 18, 2010
Reply
by: Anonymous

Thanks for the reply Bill, How would i go about finding/testing/replacing said capacitor?
I've never done it, But what I've read on here also gave me the same thought.

_____________________

Sears first, to see who fixes their compressors under warranty, and you talk to those folks. Or, any electric motor rebuild shop should be able to help.




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Craftsman 6HP 33 gal unit compressor blows fuse

by Darren
(Hopkins, MN)

I have a 7 year old Craftsman 6HP 33 gal unit that worked fine until the other day.

The compressor will run for about 2 seconds then blow the fuse.

I disconnected the feed lines to the tank and get the same result.

Being the motor spins it doesn't appear to be siezed. What other tricks can I try before I junk it?

__________________
Bill says...

You removed the line from the pump to the tank, and that should have unloaded the piston. If the tank isn't empty of air, reattach the line, and dump the tank air anyway, and try to start it again.

I'm suspecting a start capacitor issue, but I need you to rule out the unloader valve first.

Cheers,

Bill

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Jan 19, 2012
Thanks
by: Anonymous

Wow your advice for the most part useless. Advice: spend money and replace everything.. Thanks for your expert advice. Not!!!

__________________

Worth every penny you paid for it, chum!

B.

Nov 14, 2011
Same 6hp oil less compressor and problems
by: Brian H

Mine starts but does not come up to a high enough speed to drop out of the start windings. The unit is free spining, even unhooked the piston and tired it. Checked both the start and run cap. Both good. The compressor will run till the breaker trips or the overload on the motor trips. Pulling 25 - 30 amp on 120vac twice the rated current. If I push the cyntrifical swith out the current increases but no change in the motor speed. Also checked the voltage at the motor termials during running and stayed at 120VAC the entire time thus no voltage drop on my circuit. Guessing the run windings may be bad but have no way of testing. No schematic on the motor.

Nov 10, 2011
Tried replacing start capacitor
by: Anonymous

As title indicates, I tried changing start capacitor and problem does not change. I tried disconnecting the tank as well and that doesnt not help either.

Any suggestions?

___________________

The breaker pops or the fuse burns because there is too much current flowing through them. There are many things that could cause this including a marginal power supply (too many appliances pulling power from the same circuit) non-functioning unloader valve, failing capacitor, pump mechanically overloading the motor, a run capacitor failing, a motor shorting out.

If the capacitors are fine, the pump is fine, then you need to get the motor load tested, in my opinion.

Nov 03, 2011
Start Capacitor
by: Anonymous

I am having the exact same issue. My compressor keeps blowing the fuse. When I remove the cover from the switch, and turn the compressor on and off, I see lots of spark when the switch makes contact. The piston will turn but the compressor will not start going normal speed, it will start for a few seconds then blow fuse.

Where is the start capacitor located? In black box where the "pressure switch" is located? (looks like a coil from a car distributor)?

_____________________

The start and run capacitor are usually on the motor itself, a cylindrical bump on the motor housing. Depends on the compressor, of course.


Jul 27, 2011
Confirmed
by: Darren

I did initially completely empty the tank before disconnecting the line.

________________

OK. Sorry it's not the unloader valve, as that's likely a lower cost fix. As I noted in the earlier post "I'm suspecting a start capacitor issue" and you need to get it tested. Might as well get the motor load tested at the same time.


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